General Overview
The Castoridae family consists of a single living genus, Castor, which includes the North American beaver (Castor canadensis) and the Eurasian beaver (Castor fiber). Beavers are large, semiaquatic rodents renowned for their engineering skills, including building dams, lodges, and canals that dramatically alter landscapes. As ecosystem engineers, they create wetlands that support diverse plant and animal life, making them one of the most ecologically influential mammals.
Appearance
Beavers are stocky rodents with powerful bodies adapted for a semiaquatic lifestyle. They are the second-largest rodents in the world, with adults weighing between 16 and 30 kg (35–66 lbs). Their most distinctive features are their large, flat, scaly tails, which are used for swimming, balance, and warning signals, and their strong, ever-growing orange incisors, specialized for cutting through wood. They have dense, waterproof fur in shades of brown, small, rounded ears, webbed hind feet for swimming, and dexterous front paws for manipulating branches and mud.
Diet
Beavers are strict herbivores. Their diet consists mainly of the bark, leaves, and twigs of deciduous trees such as aspen, willow, birch, and cottonwood. They also feed on aquatic plants, grasses, and roots. Beavers do not eat the wood itself; instead, they consume the softer, nutrient-rich cambium layer beneath the bark. Food is often stored underwater near their lodges or dams for use during the winter months.
Habitat
Beavers inhabit freshwater environments such as rivers, streams, lakes, and ponds across much of North America, Europe, and parts of Asia. They are best known for modifying their habitats by building dams from wood, mud, and stones, which create ponds that provide protection from predators and access to food during the winter. Their lodges, constructed from branches and mud, serve as insulated homes with underwater entrances. In areas with stable water levels, beavers may instead burrow into riverbanks.
Behavior
Beavers are highly social, typically living in monogamous family groups consisting of a breeding pair and their offspring from the current and previous year. They are mainly nocturnal, spending their nights felling trees, repairing structures, and foraging. Communication occurs through scent marking, vocalizations, and dramatic tail slaps on the water to signal alarm. Beavers are industrious builders, and their activities have profound ecological effects: their dams slow water flow, reduce erosion, recharge groundwater, and create wetlands that support biodiversity.
